@article {1219,
	title = {Key role for sulfur in peptide metabolism and in regulation of three hydrogenases in the hyperthermophilic archaeon Pyrococcus furiosus.},
	journal = {J Bacteriol},
	volume = {183},
	year = {2001},
	month = {2001 Jan},
	pages = {716-24},
	abstract = {<p>The hyperthermophilic archaeon Pyrococcus furiosus grows optimally at 100 degrees C by the fermentation of peptides and carbohydrates. Growth of the organism was examined in media containing either maltose, peptides (hydrolyzed casein), or both as the carbon source(s), each with and without elemental sulfur (S(0)). Growth rates were highest on media containing peptides and S(0), with or without maltose. Growth did not occur on the peptide medium without S(0). S(0) had no effect on growth rates in the maltose medium in the absence of peptides. Phenylacetate production rates (from phenylalanine fermentation) from cells grown in the peptide medium containing S(0) with or without maltose were the same, suggesting that S(0) is required for peptide utilization. The activities of 14 of 21 enzymes involved in or related to the fermentation pathways of P. furiosus were shown to be regulated under the five different growth conditions studied. The presence of S(0) in the growth media resulted in decreases in specific activities of two cytoplasmic hydrogenases (I and II) and of a membrane-bound hydrogenase, each by an order of magnitude. The primary S(0)-reducing enzyme in this organism and the mechanism of the S(0) dependence of peptide metabolism are not known. This study provides the first evidence for a highly regulated fermentation-based metabolism in P. furiosus and a significant regulatory role for elemental sulfur or its metabolites.</p>},
	keywords = {Culture Media, Cytoplasm, Gene Expression Regulation, Archaeal, Gene Expression Regulation, Enzymologic, Glycolysis, Hydrogenase, Membrane Proteins, Oxidation-Reduction, Peptides, Pyrococcus furiosus, Sulfur},
	issn = {0021-9193},
	doi = {10.1128/JB.183.2.716-724.2001},
	author = {Adams, M W and Holden, J F and Menon, A L and Schut, G J and Grunden, A M and Hou, C and Hutchins, A M and Jenney, F E and Kim, C and Ma, K and Pan, G and Roy, R and Sapra, R and Story, S V and Verhagen, M F}
}
@article {865,
	title = {Kinetic and mechanistic characterization of the polyhydroxybutyrate synthase from Ralstonia eutropha.},
	journal = {Biomacromolecules},
	volume = {1},
	year = {2000},
	month = {2000 Summer},
	pages = {244-51},
	abstract = {Purified Ralstonia eutropha polyhydroxybutyrate (PHB) synthase from recombinant cells can exist as monomer and dimer. The polymerization reaction catalyzed by this enzyme displays a lag phase, which causes difficulties for kinetic and mechanistic characterization of the enzymatic polymerization reaction. In this study, we developed a method to eliminate the lag phase of PHB synthase by physical means, i.e., adding multihydroxyl compounds to the enzyme solution. This method allows us to recognize the nature of the lag phase as a physical rather than a chemical process. With such lag-phase-free-enzyme, the kinetic properties of the enzyme were investigated. The results indicate that 3-hydroxybutyryl-CoA (3HBCoA) is the optimal substrate for the enzyme. A slower catalytic rate and lower binding ability account for a lower reactivity of 3-hydroxyvaleryl-CoA (3HVCoA) compared to that of 3HBCoA. The change of hydroxyl group from the beta to the gamma position causes dramatic decreases in the binding ability of 4-hydroxybutyryl-CoA (4HBCoA). By using a dilution strategy and size exclusion chromatographic technique, the active form of the enzyme was identified to be the dimeric form. The number of catalytic sites in the dimeric form of the enzyme was examined by comparing the molecular weight of polyhydroxybutyrate as a function of substrate-to-enzyme ratio. The results suggest that the dimeric enzyme has only one catalytic site. A revised model of polymerization reaction catalyzed by R. eutropha PHB synthase is described.},
	keywords = {Acyltransferases, Catalysis, Chromatography, Gel, Coenzyme A, Culture Media, Hydrogen-Ion Concentration, Kinetics, Molecular Weight, Proteobacteria},
	issn = {1525-7797},
	author = {Zhang, S and Yasuo, T and Lenz, R W and Goodwin, S}
}
@article {674,
	title = {Kinetic analysis of competition between sulfate reducers and methanogens for hydrogen in sediments.},
	journal = {Appl Environ Microbiol},
	volume = {43},
	year = {1982},
	month = {1982 Jun},
	pages = {1373-9},
	abstract = {The competition between sulfate-reducing and methanogenic bacteria for hydrogen was investigated in eutrophic lake sediments that contained low in situ sulfate concentrations and in sulfate-amended sediments. Sulfate reduction and methane production coexisted in situ in lake surface sediments (0 to 2 cm), but methane production was the dominant terminal process. Addition of 10 to 20 mM sulfate to sediments resulted in a decrease in the hydrogen partial pressure and a concomitant inhibition of methane production over time. Molybdate inhibition of sulfate reduction in sulfate-amended sediments was followed by an increase in the hydrogen partial pressure and the methane production rate to values comparable to those in sediments not amended with sulfate. The sulfate reducer population had a half-saturation constant for hydrogen uptake of 141 pascals versus 597 pascals for the methanogen population. Thus, when sulfate was not limiting, the lower half-saturation constant of sulfate reducers enabled them to inhibit methane production by lowering the hydrogen partial pressure below levels that methanogens could effectively utilize. However, methanogens coexisted with sulfate reducers in the presence of sulfate, and the outcome of competition at any time was a function of the rate of hydrogen production, the relative population sizes, and sulfate availability.},
	issn = {0099-2240},
	author = {Lovley, D R and Dwyer, D F and Klug, M J}
}
